Vasoactive intestinal peptide (VIP) causes secretory diarrhea and, commensurate with its newly discovered function as a neuropeptide, is ubiquitous in human physiology. The study of receptor function and metabolism has resulted in many therapeutic gains. The candidate therefore proposes to a) characterize the affinity and distribution of the VIP receptor in rat intestine, b) study the fate of VIP after cellular binding, c) study the cellular movement and metabolism of the VIP-receptor complex, and d) isolate, purify and biochemically characterize the VIP receptor from the rat intestinal epithelial cell. VIP causes secretory diarrhea and, commensurate with its newly discovered function as a neuropeptide, is ubiquitous in human physiology. The study of receptor function and metabolism has resulted in many therapeutic gains. Any findings generated from this proposal will transcend the system studied and have wide application. The work will be sponsored by Dr. Gary M. Gray, Professor of Medicine and Head, Division of Gastroenterology at Standford and Dr. John Williams, Professor and Vice-President of the Department of Physiology at UCSF, will serve as a consultant. The research will be carried out in Dr. Gray's laboratory which has extensive experience in cellular membrane fractionational, membrane glycoprotein characterization and metabolism, and cellular physiology and molecular biology.